• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

How the heck do I get my engine running right?

Triple Black 73

Triple Black 73

Well-Known Member
Local time
6:09 PM
Joined
May 26, 2016
Messages
404
Reaction score
190
Location
Atlanta, Ga
So, I'm having a devil of a time trying find the happy timing for my engine. At 15 degrees of timing it idles good, but spitting and popping at WOT. And at 18 degrees, it surges at idle, a rocket ship at WOT but pings on the highway when going from 60 to 80 at part throttle. At 12 degrees it idle great, but it's bogs like crazy between 1k and 1.5k and chokes itself WOT, but handles the highway just fine. I can't find a happy medium! Oh, and it always runs hot.

Here's the specs of my boondoggle of an engine build:

383 bored .60 over
About 9:1 compression ratio
346 heads, no porting
Compcam XE256H
Holly Dominator Single plane intake
800 CFM Themoquad - https://www.summitracing.com/parts/sum-210234
Stock ignition
Not sure on the spark plugs. It's what RockAuto recommend for 4bbl.

I'm thinking I need 18 degrees, a larger mid range needle, and set the idle richer. But I don't know. That's why I'm asking.
 
Stock ignition? Do you mean a stock 1973 distributor, spark box, ballast resistor and coil?
If so, you may need to modify the distributor to get the car to run the way you like it. Many times, higher performance engines like MORE advance with less total timing. This means that the mechanical advance that occurs as the engine RPM increases needs to be reduced from what a stock distributor allows.
Example: If you have the initial timing set to 10 degrees and at 3000 rpms the engine shows 38 degrees, you have a 28 degree mechanical advance curve. An engine that runs great at low speeds with 18 degrees of initial timing will likely detonate at WOT because of this. The advance curve is too long.
Also, many iron head engines will knock and ping at 35 or 36 degrees unless you use really high octane race gas. This is not the only thing that leads to spark knock, camshafts factor in, as do carburetor jetting, etc.
The fix? Shorten the slots inside the distributor by welding. There are videos online, I suppose. In my case, I run 17 degrees of initial timing and 34 degrees total. That is a 17 degree advance curve. I have a Mopar Performance distributor that is easily adjustable. MSD probably has something even better.
 
Before doing anything drastic or spend any money, I would check for vacuum leaks first. If none, reinstall the distributor - going through the painful process of bringing cylinder #1 to TDC. Get the timing set. Then adjust the carb using a vacuum gauge. Make sure the distributor vacuum advance is using manifold vacuum. Retarded timing / lean fuel can both cause overheating issues.

Just out of curiosity, why the TQ from Summit?
 
I agree distributor tuning is probably in your immediate future and may fix a majority of the issues but I would question a single plane intake with the rest of your engine specs as the best choice for street response.

I have modified my distributor for 16 degrees initial advance + 20 crank degrees of centrifugal advance plus a stock vacuum advance can.
 
Have you done a plug check to see how they are burning also check all your vacuum lines could be as simple as a bad vacuum advance one step at a time check all the plugs see what color they are going 700 different directions at once isn’t going to find the problem
 
I have not tried it yet. But I have seen a limiter plate that can be installed in the distance. That has different slots for different degrees.
Can somebody share any personal experience on these?
I have weld ed d the slots, it requires some trial and error.
 
The plate is simple and worth it. You need to limit total timing otherwise you will keep going in circles.

Set base timing where you get close to best / highest vacuum first. Then adjust your total. The mechanical advance in the distributor is stamped with a number, times that number by 2 to get the mechanical advance. Add base timing and mechanical timing to get total, B engine should be in the neighborhood of 36-37 degrees total.
 
may be making too much cylinder pressure with that short intake lobe (intake is closing at 54 degrees ABDC; even with 9:1 compression. if that's the case than having an aggressive timing curve may aggravate the situation. a lean condition either from carb calibration or low fuel pressure/volume will make matters worse. it's a juggling act sometimes.
 
lewtot184 said:
may be making too much cylinder pressure with that short intake lobe (intake is closing at 54 degrees ABDC; even with 9:1 compression. if that's the case than having an aggressive timing curve may aggravate the situation. a lean condition either from carb calibration or low fuel pressure/volume will make matters worse. it's a juggling act sometimes.
Click to expand...
This is why the diag is step by step eliminating any possible issues to find the one that is causing the problem.I was thinking more along the too lean possibility......
 
HEMI-ITIS said:
When did this start? Was this carb in use and running right before you had this issue.
Click to expand...

Since day one. We initially had it set to 7 degrees as the old book said. That made it run like complete junk. I chased the timing to 12 degrees to get it to run decent. The single plane required 15 to 16 to run right. I added it because the dual plane produced so much torque at low rpm that the car was undriveable. As in just touching the gas at 2k would spin the tires or idle up a hill. It was crazy. The single actually makes the engine run like I want at low RPM and produce the power I want at high rpm. Well, other than the timing being all over the place.

I think the other guys is one the right track. When total advance is set to 38 it runs great at WOT and on the highway, but junk at idle. Some guy at a car show said he had similar issues with the stock vacuum distributor. Switching over to a MSD digital cleared up the issue. But that thing is over 500 bucks! There is a MSD mechical advance on Craigslist for $100. Maybe I'll get that?
 
Just my two cents, but I’ve read that the ignition module in the Unilite distributors is very sensitive to voltage spikes and dips, and you should add in a circuit guard to protect it, like this one:
https://www.summitracing.com/parts/maa-29371
It’s a bit of a disservice in my mind that Summit does not at least show this in the “Suggested Parts” tab under the description for the distributor. Nor is it shown in any of the wiring diagrams for the distributor from Mallory.

I bought a used one of these years ago before I realized it needed the circuit protection and a ballast resistor. My intent was to build an ignition that was more bulletproof and stable than the factory stuff. But it just gave me an uneasy feeling that it was so sensitive to voltage dips and spikes.

Anyway, I just wanted to throw that in there so you have the option to get this before you have an issue with the module.
 
Last edited:
I think I figured out what's going on, and it's never just one thing. There wasn't enough advance, and the cap was burned up, and the #7 spark plug cable was jumping to the steering shaft. Yeah, the cable tested fine on the bench but if the cable got to close to the steering shaft if would jump to the shaft. I could left up the cable and the car ran fine but if it got to close, it would jump and the engine would run like crap. There was a wear mark on the cable from the shaft. I'll redo the cable and reroute it so it's not touching anything.
 
I had my crash coarse in timing not so long ago, talk about wanting to pull your hair out!!:BangHead: My situation sounded much like yours with me finding the happy spot at both idle and WOT but never finding the happy medium which. Thanks to FBBO members and Don at FBO I got it dialed in and have been racking up miles every since.

Outside of the curve what I ended up doing was setting the initial at 20 degrees then set the vacuum advance for an additional 10 degrees hooked to manifold vacuum and set total at 40. At 20 degrees my car cranks over great but is a complete dog off the line, the additional 10 degrees as soon as the engine starts really found that happy medium without added more total.

If you get stumped I wouldn't hesitate to talk to Don, he offers many services in regards to ignition and is very knowledgeable.
 
Triple Black 73 said:
I think I figured out what's going on, and it's never just one thing. There wasn't enough advance, and the cap was burned up, and the #7 spark plug cable was jumping to the steering shaft. Yeah, the cable tested fine on the bench but if the cable got to close to the steering shaft if would jump to the shaft. I could left up the cable and the car ran fine but if it got to close, it would jump and the engine would run like crap. There was a wear mark on the cable from the shaft. I'll redo the cable and reroute it so it's not touching anything.
Click to expand...
Hope that's it:thumbsup:. I had a set of MSD wires that wouldn't quit falling off, finally trashed them for Taylor wires. These problems almost always uncover many little things before you nail them down. Good luck.
 
2 things,1st I use the MSD 6al-2 which is programmable with a laptop,
2nd is I went from MSD wires to Firecore,best wire I have ever used!
 
If there are wire that are arcing to other components, then maybe replace the set with quality ones. Another vote for Taylor.
 
You must log in or register to reply here.

Similar threads

Polyhead
Dual Carter AFB Bog and Stall Issue on WOT Acceleration - 413 Max Wedge
2
Replies
34
Views
2K
Polyhead
Polyhead
Mark1972
How hard on engine and driveline is this?
2
Replies
29
Views
2K
Butch Harley
Butch Harley
glrestomod
1970 383 in 1969 Charger Not Running Right
3 4 5
Replies
87
Views
4K
glrestomod
glrestomod
furious70
Struggling to find the right oil pressure balance
2 3
Replies
48
Views
4K
Fran Blacker
Fran Blacker
D
Timing mark jumping around
Replies
19
Views
2K
Black_Sheep
Black_Sheep
Auto Transport Service
Back
Top